Why hdlc

HDLC High-level Data Link Control is a group of protocols or rules for transmitting data between network points sometimes called nodes. The data link layer is the protocol layer in a program that handles the moving of data into and out of a physical link in a network. The data link layer also determines how devices recover from collisions that may occur when nodes attempt to send frames at the same time.

HDLC is basically a group of data link layer protocols of the Open System Interconnection OSI Model that is required to transmit synchronous data packets or frames among point-to-point nodes. It also provides both connection-oriented service and connectionless service. These type of frame are used to provide the reliable data link service. Two types of numbered frames are supported: S supervisory frames containing only an acknowledgment number N R I information frames carrying data and containing both a send sequence number N S and an acknowledgment number N R.

There are 5 different fields in the HDLC frame. Control field defines the frame types. The functions provided by other fields are more specific and are discussed in this section. Flag is an 8-bit pattern that uniquely identifies the start or end of a frame. HDLC is a simple protocol used to connect point to point serial devices.

Computers use PPP to communicate over the telephone network or the Internet. A PPP connection exists when two systems physically connect through a telephone line. You can use PPP to connect one system to another. PPP also supports multiple protocols and support authentication.

Advantages of PPP 3. If too many errors are detected, PPP takes the link down. Why hdlc is used? Asked by: Shea Littel V. What is HDLC protocol and its features? Who has defined the HDLC? What is HDLC frame format?

If it is sent by the secondary station, it contains the address of the primary station. The address field may be from 1 byte to several bytes. Its length may vary from one network to another. The standard code used is CRC cyclic redundancy code.

There are three types of HDLC frames. They also include flow and error control information that is piggybacked on user data.

The first bit of control field of I-frame is 0. They are used for flow and error control when piggybacking is not required. The first two bits of control field of S-frame is It may contain an information field, if required. The first two bits of control field of U-frame is Nishtha Thakur.